1. Field of the Invention
This application relates generally to a seal to be provided to an oxidation oven for minimizing the release of process gases from the oxidation oven into an ambient environment and, more specifically, to an end seal disposed externally of a vestibule chamber that captures process gases from an oven chamber and minimizes cold air infiltration into the oven chamber.
2. Description of Related Art
Conventional end seals such as that disclosed in U.S. Pat. No. 6,776,611 and used on oxidation ovens counter the oven process gas losses in the upper product slots due to the natural pressure increase inside the oven chamber, an effect referred to as the “chimney effect.” However, conventional end seals tend to introduce significant amounts of air having a temperature that is significantly less than the temperature of process gases used to treat product fibers within the oven chamber. The relatively-cool air introduced into the oven chamber can result in temperature gradients that can potentially cause non-uniformities across the product fibers. Further, process gases exposed to the relatively-cool air introduced by the end seals are prone to condensing within the oven chamber and forming a condensate referred to as “tar.” Tar can accumulate within the oven chamber and degrade performance of the end seals. Thus, tar is removed periodically, requiring the oxidation oven to be shut down for a period during which production is lost.
To minimize the discharge of process gases into an ambient environment of the oxidation oven, a vestibule has typically been provided to an external side of the end seal, separated from the oven chamber by the end seal. However, the fiber passes repeatedly enter and exit the vestibule to be routed through the oven chamber, thereby elevating the temperature within the vestibule. The elevated temperature in the vestibule causes an elevated pressure therein that can force air out of the vestibule into the ambient, lower-pressure environment. To counter this problem, conventional oxidation ovens typically increase the rate at which the gases are exhausted from the vestibule and delivered to a scrubber or other treatment system for disposing of the exhausted process gases. However, the greater the rate at which the process gases are exhausted from the vestibule the greater the amount of process gases that must be treated for disposal. And while lowering the temperature within the conventional vestibule can minimize the pressure rise, such a condition promotes the undesirable formation of tar therein.